This randomized controlled clinical trial aims to evaluate the clinical performance of 3D-printed composite resin restorations compared with semi-direct composite resin restorations in posterior teeth requiring Class II inlay or onlay restorations.

Dental restorations are commonly used to restore teeth affected by caries or structural defects. Advances in digital dentistry have introduced three-dimensional (3D) printing technologies that enable the fabrication of indirect composite resin restorations with improved precision, efficiency, and reproducibility. Semi-direct composite resin restorations represent another conservative restorative approach that combines the advantages of direct and indirect techniques while reducing polymerization shrinkage and improving anatomical form.

Although both techniques are increasingly used in clinical practice, evidence regarding their long-term clinical performance remains limited. Therefore, this randomized controlled clinical trial aims to compare the clinical performance of 3D-printed composite resin restorations and semi-direct composite resin restorations in posterior teeth requiring Class II inlay or onlay restorations.

Sixty patients aged 25 to 40 years who require two Class II inlay or onlay restorations will be enrolled by invitation from patients attending the Faculty of Dentistry, Tanta University. Participants will be randomly allocated into two groups according to the restorative material and fabrication technique used. Group I will receive 3D-printed composite resin restorations, while Group II will receive semi-direct composite resin restorations.

All cavity preparations and restorative procedures will be performed according to standardized clinical protocols and manufacturers' instructions. Clinical evaluations will be conducted at baseline, 6 months, 9 months, and 12 months after restoration placement using the modified FDI World Dental Federation criteria.

The primary objective is to evaluate the overall clinical performance and survival of the restorations over a 12-month follow-up period. Secondary outcomes include assessment of retention, marginal integrity, surface roughness, anatomical form, postoperative sensitivity, and the occurrence of secondary caries.

The findings of this study will contribute to the evidence regarding the effectiveness and clinical reliability of 3D-printed composite resin restorations compared with semi-direct composite resin restorations and may support clinical decision-making in restorative dentistry.

Inclusion Criteria:

• Patients aged 25-40 years.
• Patients requiring two Class II inlay or onlay restorations.
• Teeth with carious lesions or defective restorations requiring indirect restorative treatment.
• Teeth with sufficient structure to receive an inlay/onlay restoration.

Exclusion Criteria:

• Patients with systemic diseases or medical conditions that may affect oral health or healing.
• Pregnant or lactating patients.
• Patients with poor oral hygiene or uncontrolled periodontal disease.